This application claims the priority of German patent document 100 32 666.8, filed 5 Jul. 2000 (PCT International Application No. PCT/EP01/07546, filed 2 Jul. 2001), the disclosure of which is expressly incorporated by reference herein.
The invention relates to an audio system for a motor vehicle.
In a vehicle having multiple audio signal sources, such as a radio, cassette player, CD player, etc, it is known to use the audio speaker units installed in the vehicle for a mobile telephone hands-free device as well. For this purpose, the audio signal source is turned off when a signal is received from the mobile telephone, and the mobile telephone is connected to the speaker units in the vehicle by means of a changeover unit. When the call has ended, the previous audio signal source is again connected to the speaker units.
U.S. Pat. No. 5,420,931 discloses an audio system that includes entertainment systems of varying quality. (In this case, an entertainment system comprises an audio source and an amplifier.) Audio outputs from the high-quality entertainment system, comprising a high-quality audio source and a high-quality amplifier, can be output on all the vehicle speakers or on a subset thereof. It is also possible for audio outputs from the lower-quality entertainment system, comprising a lower-quality audio source and a lower-quality amplifier, to be output on all the vehicle speakers or on a subset thereof. The two systems exist side by side with equal rights. That is, provision is also made for audio signals from one entertainment system to be output on one subset of the vehicle speakers and for audio signals from the other entertainment system to be output simultaneously on the other subset of the vehicle speakers.
German patent document DE 38 28 634 A1 discloses a speaker having two oscillating coils which allows information and warnings to be output on the speaker in addition to an audio signal source. In addition, German patent document DE 38 42 417 A1 discloses an audio system which allows audio messages from a voice memory to be output on speakers; and German patent document DE 42 12 337 A1 discloses a safety system in a vehicle comprising anti-lock protection or traction control systems and restraining systems. It describes redundancy in the form of identical duplicate performance of arithmetic operations.
It is an object of the invention to provide an audio system for a motor vehicle which allows one particular audio signal source or a plurality of particular audio signal source in the vehicle to be reproduced with a very high level of reliability and availability.
This and other objects and advantages are achieved by the audio system according to the invention, which utilizes a multiple design of the connection between a particular audio signal source and a speaker unit, with the high-quality amplifier unit for the primary supply designed redundantly in the secondary supply in the form of an amplifier unit which is provided only for emergencies. Such redundant design makes it possible for audio signals to be reliably output on at least one speaker in an emergency or in an accident situation, for example. This is used, by way of example, to make at least one speaker reliably available to the voice link between an emergency-call center and the vehicle occupants. Alternatively, audio signals can be information/warning tones for the driver which he can hear even if the main part of the audio system has failed.
In one embodiment of the audio system according to the invention, a function check is performed on the primary supply between audio signal source and speaker unit, and the secondary supply is used only if the primary supply has been determined to be faulty. This function check allows the secondary supply to be specifically actuated when required, preventing a reduction in the sound quality or mixing of sources in the normal situation, because the secondary supply is entirely unused in that case.
Another embodiment of the audio system according to the invention, allows reproduction of the particular audio signal source in the best available quality by using, for example, all the speakers in the available audio system (provided that the audio system is still operational) to output the voice link to the emergency-call center. In many cases, the main system will still be operational after an emergency call has been sent, since the latter does not always mean that an accident has occurred. Breakdown could also be the reason for the emergency call, for example. In a breakdown situation, the main system is generally still operational and its high quality can also be used for voice reproduction in an emergency. In this context, the invention affords the advantage that no additional speakers need to be installed for emergency calls, thus reducing both vehicle cost and weight, and saving on installation space as well. For these reasons, dedicated speakers for emergency calls are usually small and are designed to have lesser sound properties. The invention also uses the high-quality main system in an emergency if it is still operational at that time; and even if not, a regular high-quality speaker in the main system is used via the secondary supply in emergencies. This has the overall result of improved sound quality in emergencies.
According to another embodiment of the invention, the function check on the primary supply can be performed at regular intervals, and the secondary supply can be used to output important information if the primary supply is faulty. Such information may comprise, for example, traffic reports, driving instructions from a navigational unit or warning and information tones.
In another advantageous embodiment of the invention, changeover between primary supply and secondary supply is effected by a changeover unit. Such an implementation does not impair the reproduction of the rest of the audio signal sources, since it is possible to dispense with dual-coil speakers. A changeover unit can comprise a control unit and one or more electromechanical or electronic changeover switches.
In still another embodiment of the invention, there is at least one amplifier unit between the audio signal sources and the speaker units, the primary supply between audio signal sources and the amplifier unit being in the form of a data bus. The fact that the primary supply is in the form of a data bus reduces the wiring complexity, and hence the cost and weight of a vehicle. Normally, audio systems use data buses designed for entertainment purposes which have a high level of flexibility and transmission capacity in the foreground. This is where the invention of designing the supply to the amplifier unit to be redundant is particularly advantageous, since the audio signal reaches the amplifier via the secondary supply if the data bus is not working. In this way, such data buses are provided with the reliability and availability necessary for emergencies or warning information.
By installing the audio source, amplifier unit and/or speaker unit at particularly secure locations, the reliability and availability of the audio system are further enhanced.
Finally, according to yet another embodiment of the invention the speaker units are in redundant form, which is particularly beneficial for their use in emergencies, because it further enhances the reliability of the system. This can be achieved, for example, by virtue of the audio signals being supplied to a plurality of speakers at the same time, so that they are output via the intact speaker units every time. Alternatively, it can be achieved by performing a function check on the speaker prior to the supply of an audio signal to it. The audio signal is then output on an operational speaker unit, for example.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.